2,312 publications from this institution
This paper proposes an event-triggered variational Bayesian filter for remote state estimation with unknown and time-varying noise covariances. After presetting multiple nominal process noise covariances and an initial measurement noise covariance, a variational Bayesian method and a fixed-point iteration method are utilized to jointly estimate the posterior state vector and the unknown noise covariances under a stochastic event-triggered mechanism. The proposed algorithm ensures low communication loads and excellent estimation performances for a wide range of unknown noise covariances. Finally, the performance of the proposed algorithm is demonstrated by tracking simulations of a vehicle.
Bifurcation control generally means to design a controller that is capable of modifying the bifurcation characteristics of a bifurcating nonlinear system, thereby achieving some desirable dynamical behaviors. A typical objective is to delay and/or stabilize an existing bifurcation. In this paper, we consider the problem of anti-controlling bifurcations, that is, a certain bifurcation is created at a desired location with preferred properties by appropriate control. Washout-filter-aided dynamic feedback control laws are developed for the creation of Hopf bifurcations. As Hopf bifurcations give rise to limit cycles, anti-control of Hopf bifurcations suggests a new approach for designing limit cycles with specified oscillatory behaviors into a system via feedback control when such dynamical behaviors are desirable,.
In this paper <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> , we propose a novel cooperative scheme to enhance the performance of multiple-access (MA) differential-chaos-shift-keying (DCSK) systems. We provide the bit-error-rate (BER) performance and throughput analyses for the new system with a decode-and-forward (DF) protocol over Nakagami-m fading channels. Our simulated results not only show that this system significantly improves the BER performance as compared to the existing DCSK non-cooperative (DCSK-NC) system and the multiple-input multiple-output DCSK (MIMO-DCSK) system, but also verify the theoretical analyses. Furthermore, we show that the throughput of this system approximately equals that of the DCSK-NC system, both of which have prominent improvements over the MIMO-DCSK system. We thus believe that the proposed system can be a good framework for chaos-modulation-based wireless communications.
Recently, it has been demonstrated that many large-scale complex dynamical networks display a collective synchronization motion. Here, we introduce a time-varying complex dynamical network model and further investigate its synchronization phenomenon. Based on this new complex network model, two network chaos synchronization theorems are proved. We show that the chaos synchronization of a time-varying complex network is determined by means of the inner coupled link matrix, the eigenvalues and the corresponding eigenvectors of the coupled configuration matrix, rather than the conventional eigenvalues of the coupled configuration matrix for a uniform network. Especially, we do not assume that the coupled configuration matrix is symmetric and its off-diagonal elements are nonnegative, which in a way generalizes the related results existing in the literature.
A secure digital communication system based on chaotic theory is proposed that can resist intrusion of eavesdroppers during the transmission of signals and data. With the master-slave M-synchronization technique, the transmitter and the receiver are designed using the chaotic phase shift keying. Further increasing the complexity of the chaotic dynamics for higher security, a new discrete-time n-scroll attractor model is built based on Chua's circuit. This methodology for designing secure communication systems can, in principle, be well applied to most on-line communication applications, such as Internet telephone, e-commerce transactions, and digital data transfer.
An efficient image encryption algorithm is proposed, based on image reconstruction using some adjacent pixel characteristics. Since the permutation of sub-images composing of high 4-bits of the original image has a relatively high computational complexity, in the new scheme the permutation of sub-images is performed with low 4-bits instead, which therefore has a lower computational complexity. Experiment has been carried out, showing relatively high efficiency and security of the new cryptosystem.
This paper presents some unusual dynamics of the Rabinovich-Fabrikant system, such as "virtual" saddles, "tornado"-like stable cycles and hidden chaotic attractors. Due to the strong nonlinearity and high complexity, the results are obtained numerically with some insightful descriptions and discussions.
This paper is concerned with a class of finite-dimensional discrete spatiotemporal systems of the form { x 1 ( m + 1 , n ) = f 1 ( x 1 ( m , n − 1 ) , x 1 ( m , n ) , x 2 ( m , n ) , … , x k ( m , n ) , x 1 ( m , n + 1 ) ) x 2 ( m + 1 , n ) = f 2 ( x 2 ( m , n − 1 ) , x 1 ( m , n ) , x 2 ( m , n ) , … , x k ( m , n ) , x 2 ( m , n + 1 ) ) ⋯ ⋯ ⋯ ⋯ x k ( m + 1 , n ) = f k ( x k ( m , n − 1 ) , x 1 ( m , n ) , x 2 ( m , n ) , … , x k ( m , n ) , x k ( m , n + 1 ) ) , where k > 0 is an integer, f i : R k + 2 → R is a real function for all i = 1 , 2 , … , k , m ∈ N 0 = { 0 , 1 , 2 , … } and n ∈ Z = { … , − 1 , 0 , 1 , … } (or, n ∈ N 0 in some special cases). Definitions of chaos of this system in the sense of Devaney and of Li–Yorke are given. Some sufficient conditions for this system to be stable and some illustrative examples for this system to be chaotic in the sense of Devaney and of Li–Yorke, respectively, are derived.
A complex networked system typically has a time-varying nature in interactions among its components, which is intrinsically complicated and therefore technically challenging for analysis and control. This paper investigates an epidemic process on a time-varying network with a time delay. First, an averaging theorem is established to approximate the delayed time-varying system using autonomous differential equations for the analysis of system evolution. On this basis, the critical time delay is determined, across which the endemic equilibrium becomes unstable and a phase transition to oscillation in time via Hopf bifurcation will appear. Then, numerical examples are examined, including a periodically time-varying network, a blinking network, and a quasi-periodically time-varying network, which are simulated to verify the theoretical results. Further, it is demonstrated that the existence of time delay can extend the network frequency range to generate Turing patterns, showing a facilitating effect on phase transitions.
This paper presents some new and explicit stability results for Volterra systems from two different approaches. The first approach is based on monomial domination of the Volterra system's memoryless output nonlinearity and the second on its Lipschitz-norm. The former yields more widely applicable results, but introduces nonconvexity in the signal spaces for certain parameter values.
